In recent years, as a next generation high efficiency illumination light source, a white LED (light emitting diode) has been put into a practical use instead of an incandescent lamp or a fluorescent lamp. The white LED has been combined with a blue LED and a yellow phosphor, and further with e.g. a red phosphor as the case requires, so as to be adjusted to daylight white or bulb-color. In order to protect an LED device from external physical and chemical actions, an LED package has been encapsulated with a light-transmitting resin, such as a silicone resin. However, light sources requiring a high output power, such as headlights for automobiles, may deteriorate the light-transmitting resin used for encapsulation, since light emitted from the device has a very high energy density and further the surface of the device becomes a high temperature due to heat generation. If the light-transmitting resin is thus deteriorated, the light emitting output will decrease, and the lifetime as a light source will be short. Further, in recent years, an UV-LED having a higher output power has been more utilized as a light source as an alternative to a mercury lamp, but there are no ultraviolet-ray resistant resin at present.
Patent Documents 1 and 2 have proposed a liquid-state curable fluorinated polymer having a CF2═CFO— (perfluorovinyl ether) group, which is thermally cured or UV cured to obtain a cured product excellent in heat resistance or light resistance.